In a dense human populated area in the pub region you make phone calls to find your friend. Clog the phone networks and can't get through. Why not use the people not making a call to route your call ? Give them call credits if you use them as a hop.
The telco provider system creates a star topology where all calls have to pass through the base station. With the proliferation of wireless capable phones, this topology can be converted into a mesh-topology and reused to provide social phone calls.